JP5947192B2 - Rubber wet masterbatch production method, rubber wet masterbatch, and rubber composition containing rubber wet masterbatch - Google Patents

Description

  The present invention relates to a method for producing a rubber wet masterbatch obtained by using at least a filler, a dispersion solvent, and a rubber latex solution as raw materials, a rubber wet masterbatch, and a rubber composition containing the rubber wet masterbatch, particularly rubber. The present invention relates to a method for producing a rubber wet masterbatch that is excellent in elongation at break and excellent tear resistance, a rubber wet masterbatch produced by the production method, and a rubber composition containing the rubber wet masterbatch. .

  Conventionally, in the rubber industry, it has been known to use a rubber wet masterbatch in order to improve the processing performance and the dispersibility of a filler when producing a rubber composition containing a filler such as carbon black. Yes. This is because the filler and the dispersion solvent are mixed in advance at a certain ratio, and the filler-containing slurry solution in which the filler is dispersed in the dispersion solvent by mechanical force and the rubber latex solution are mixed in the liquid phase. Thereafter, the solidified product obtained by adding a coagulant such as an acid is recovered and dried. When using a rubber wet masterbatch, compared to using a rubber dry masterbatch obtained by mixing the filler and rubber in a solid phase, the dispersibility of the filler is superior, and rubber properties such as processing performance and reinforcement performance A rubber composition having excellent resistance is obtained. By using such a rubber composition as a raw material, for example, a rubber product such as a pneumatic tire with reduced rolling resistance and excellent fatigue resistance can be produced.

  In the method for producing a rubber wet masterbatch described above, a method for removing water derived from the dispersion solvent and the rubber latex solution from the filler-containing rubber coagulated product obtained after the coagulation step is, for example, a solid-liquid method by a filtration method or a centrifugal separation method. An example is a method of performing dehydration by performing kneading while heating the filler-containing rubber coagulated product using an arbitrary mixer after the separation. In such a dehydration method, the water content of the rubber wet masterbatch obtained after dehydration can be reduced as the number of steps such as dehydration, drying and plasticization is increased or the heating temperature at the time of kneading is increased. However, if the number of steps such as dehydration, drying, plasticization, the amount of heat and / or mechanical energy applied during dehydration increases, the resulting rubber composition of the rubber wet masterbatch will be broken and the rubber composition finally obtained The vulcanized rubber properties of the product may deteriorate.

  In the following Patent Document 1, a rubber wet masterbatch containing a rubber component and a filler is dried and kneaded while using a twin screw extruder as a first kneader, and then a second kneader Banbury mixer is used. And a method for producing a rubber chemical-containing masterbatch characterized by further mixing a rubber chemical. However, in such a production method, a rubber wet masterbatch is produced by drying and kneading the filler-containing rubber coagulum using a twin-screw extruder, so that the mechanical energy imparted to the rubber wet masterbatch is increased. It tends to increase and cause deterioration of the rubber component. Therefore, there is a tendency that the final tear resistance of the vulcanized rubber and the stress characteristics in the high strain region are deteriorated.

  In the following Patent Document 2, the mastication step is performed while applying mechanical energy of at least about 0.3 MJ / kg (about 249 W / kg) to the rubber coagulated product obtained after the dehydration step. A method for producing an elastomer composite is described in which an additional mastication step is performed while applying mechanical energy of 0.9 MJ / kg (about 83 W / kg). However, even in such a production method, the mechanical energy imparted to the rubber wet masterbatch tends to increase, and the rubber component tends to deteriorate. Furthermore, by performing the dehydration / drying process a plurality of times, the tendency of the rubber component to deteriorate is increased. Therefore, there is a tendency that the final tear resistance of the vulcanized rubber and the stress characteristics in the high strain region are deteriorated.

JP 2010-65126 A Special table 2011-511148 gazette

  The present invention has been made in view of the above circumstances, and its purpose is to manufacture a rubber wet masterbatch that is excellent in elongation at break and tear resistance, in which deterioration of the rubber is suppressed, and the manufacturing method. Another object of the present invention is to provide a rubber wet masterbatch and a rubber composition containing the rubber wet masterbatch.

  The above object can be achieved by the present invention as described below. That is, the present invention relates to a method for producing a rubber wet masterbatch obtained using at least a filler, a dispersion solvent, and a rubber latex solution as raw materials, the slurry solution containing the filler and the dispersion solvent, and the rubber latex. A solidification step of producing a filler-containing rubber coagulum by mixing and coagulating the solution, and heating to 180-200 ° C. using a single screw extruder, thereby dehydrating the filler-containing rubber coagulum. A heating step for performing drying and plasticization in one step, and the single-screw extruder has an outer wall in which a screw and a slit extending along the outer cylinder length direction (screw axis direction) are formed on the inner wall surface. The present invention relates to a method for manufacturing a rubber wet masterbatch, characterized in that at least a part of the inner wall surface of an outer cylinder is blasted.

  According to the above production method, a slurry solution containing a filler and a dispersion solvent and a rubber latex solution are mixed and coagulated to produce a filler-containing rubber coagulum (coagulation step). Drying and plasticization are performed in one step (heating step). Therefore, since the number of heating steps is reduced as compared with the conventional techniques for performing dehydration, drying and plasticization, rubber deterioration can be suppressed, and a rubber wet masterbatch excellent in elongation at break and tear resistance can be produced. . In such a heating process, a single screw extruder is used and heated to 180 to 200 ° C. When the heating temperature is less than 180 ° C., the moisture content is not sufficiently reduced, and the filler during extrusion is used. Since the viscosity of the contained rubber coagulum becomes high, plasticization may be insufficient. On the other hand, when the heating is higher than 200 ° C., the rubber may be deteriorated due to an excessive heat history.

  In the above manufacturing method, a single-screw extruder having a screw and an outer cylinder is used, and the outer cylinder has a slit formed on the inner wall surface along the outer cylinder length direction (screw axis direction). It is characterized by the fact that at least a part of the inner wall surface of the outer cylinder is blasted. When a heating process is performed using a single-screw extruder having such an outer cylinder, a filler is contained between the blasted surface of the inner wall surface of the outer cylinder having a micro roughness (fine irregular shape) and the screw. Since the shearing force acts on the rubber coagulated product, the filler-containing rubber coagulated product is caught in the fine uneven shape and receives the shearing force. As a result, it is estimated that the filler-containing rubber coagulated material can be efficiently dehydrated, dried and plasticized in one step. As described above, since the dehydration / drying / plasticization can be performed efficiently, the manufacturing method according to the present invention has a plurality of steps (dehydration / drying / plasticization) applied to the filler-containing rubber coagulated material as compared with the prior art. ) Can be performed in one step, and the heat and mechanical energy imparted to the filler-containing rubber coagulum can be reduced. As a result, it is possible to produce a rubber wet masterbatch in which deterioration of rubber is suppressed and excellent in elongation at break and tear resistance.

  In the method for producing a rubber wet masterbatch, the surface roughness (Ra) of the blasted surface of the inner wall surface of the outer cylinder is preferably 10 to 100 μm. According to this configuration, since a shearing force acts between the blasted surface of the inner cylinder inner wall surface having a suitable surface roughness and the screw, the shearing force is more efficiently applied to the filler-containing rubber coagulum. Works. Therefore, the heat and mechanical energy imparted to the filler-containing rubber coagulated product can be further reduced, so that the deterioration of the rubber can be further suppressed.

The present invention relates to a rubber wet masterbatch produced by any one of the production methods described above, and particularly relates to a rubber composition containing the rubber wet masterbatch. The vulcanized rubber obtained by vulcanizing such a rubber wet masterbatch and a rubber composition is suppressed in rubber deterioration and excellent in elongation at break and tear resistance. From the viewpoint of handling the rubber wet masterbatch and the influence during kneading, the rubber wet masterbatch preferably has a void volume of 2 to 15%. The “porosity of rubber wet masterbatch” can be calculated from the following equation.
(Porosity (%)) = 100 × ((Measured rubber wet masterbatch volume) − (Theoretical rubber wet masterbatch)) / (Measured rubber wet masterbatch volume)
However, (theoretical rubber wet masterbatch volume) = (rubber wet masterbatch weight) / (theoretical rubber wet masterbatch specific gravity)

An example of an external view of a single screw extruder usable in the present invention AA arrow sectional view of FIG. Example of development of inner wall surface of outer cylinder

  The method for producing a rubber wet masterbatch according to the present invention includes at least a solidification step and a heating step. Each step will be described below.

(Coagulation process)
In the coagulation step, a slurry solution containing a filler and a dispersion solvent and a rubber latex solution are mixed and coagulated to produce a filler-containing rubber coagulum. In particular, in the coagulation step, when the filler is dispersed in the dispersion solvent, a step of producing a slurry solution containing the filler to which the rubber latex particles are adhered by adding at least a part of the rubber latex solution (I ), The slurry solution, and the remaining rubber latex solution to produce a filler-containing rubber latex solution to which rubber latex particles are adhered, and a filler-containing rubber latex to which rubber latex particles are adhered. It is preferable to have a step (III) of coagulating the solution to produce a filler-containing rubber coagulated product.

  In the present invention, the filler means an inorganic filler usually used in the rubber industry, such as carbon black, silica, clay, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide. Among the inorganic fillers, carbon black can be particularly preferably used in the present invention.

  As carbon black, for example, conductive carbon black such as acetylene black and ketjen black can be used in addition to carbon black used in ordinary rubber industry such as SAF, ISAF, HAF, FEF, and GPF. The carbon black may be a granulated carbon black or a non-granulated carbon black granulated in the normal rubber industry in consideration of its handleability.

  As the dispersion solvent, it is particularly preferable to use water, but for example, water containing an organic solvent may be used.

  Natural rubber latex solution and synthetic rubber latex solution can be used as the rubber latex solution.

  The natural rubber latex solution is a natural product produced by the metabolic action of plants, and a natural rubber / water system is particularly preferred in which the dispersion solvent is water. The number average molecular weight of the natural rubber in the natural rubber latex used in the present invention is preferably 2 million or more, and more preferably 2.5 million or more. Examples of the synthetic rubber latex solution include those produced by emulsion polymerization of styrene-butadiene rubber, butadiene rubber, nitrile rubber, and chloroprene rubber.

  Hereinafter, an example of a preferable coagulation step will be described based on an example in which a natural rubber latex solution is used as the filler and carbon black and a rubber latex solution. In this case, it is possible to produce a rubber wet masterbatch in which the degree of dispersion of carbon black is very high and the low heat generation performance, durability performance and rubber strength are further improved when vulcanized rubber is used. Natural rubber latex can be used without distinction, such as concentrated latex and fresh latex called field latex.

  In addition, in the manufacturing method of the rubber wet masterbatch which concerns on this invention, it is not necessary to use the additive called the viscosity stabilizer for the purpose of suppression of the viscosity rise in the storage initial stage of a rubber wet masterbatch. Examples of the viscosity stabilizer include hydrazide compounds such as acetic acid hydrazide, propionsan hydrazide, butyric acid hydrazide, caproic acid hydrazide, cyclopropyl hydrazide; sulfated hydroxylamine; semicaribazide; And so on.

(1) Step (I)
In step (I), when carbon black is dispersed in a dispersion solvent, a slurry solution containing carbon black to which natural rubber latex particles are adhered is produced by adding at least a part of the natural rubber latex solution. The natural rubber latex solution may be mixed with a dispersion solvent in advance, and then carbon black may be added and dispersed. Alternatively, carbon black may be added to the dispersion solvent, and then carbon black may be dispersed in the dispersion solvent while adding the natural rubber latex solution at a predetermined addition rate, or carbon black may be added to the dispersion solvent. Then, carbon black may be dispersed in a dispersion solvent while adding a certain amount of natural rubber latex solution in several times. By dispersing carbon black in the dispersion solvent in the presence of the natural rubber latex solution, a slurry solution containing carbon black with natural rubber latex particles attached thereto can be produced. The amount of the natural rubber latex solution added in the step (I) is 0.075 to 12% by mass with respect to the total amount of the natural rubber latex solution used (the total amount added in the step (I) and the step (II)). Illustrated.

  In the step (I), the amount of solid content (rubber) of the natural rubber latex solution to be added is preferably 0.25 to 15% by mass ratio with respect to carbon black, and preferably 0.5 to 6%. preferable. Moreover, it is preferable that the solid content (rubber) density | concentration in the natural rubber latex solution to add is 0.2-5 mass%, and it is more preferable that it is 0.25-1.5 mass%. In these cases, it is possible to produce a rubber wet masterbatch in which the degree of dispersion of carbon black is increased while reliably attaching the natural rubber latex particles to the carbon black.

  In the step (I), as a method of mixing carbon black and a dispersion solvent in the presence of a natural rubber latex solution, a high shear mixer, a high shear mixer, a homomixer, a ball mill, a bead mill, a high pressure homogenizer, an ultrasonic homogenizer, a colloid mill, etc. And a method of dispersing carbon black using a general disperser.

  The "high shear mixer" is a mixer having a rotor and a stator, and the rotor rotates with a precise clearance between a rotor capable of high-speed rotation and a fixed stator. Means a mixer with a high shearing action. In order to produce such a high shearing action, it is preferable that the clearance between the rotor and the stator is 0.8 mm or less and the circumferential speed of the rotor is 5 m / s or more. A commercial item can be used for such a high shear mixer, for example, “High Shear Mixer” manufactured by SILVERSON.

  In the present invention, carbon black and a dispersion solvent are mixed in the presence of a natural rubber latex solution to produce a slurry solution containing carbon black to which natural rubber latex particles are adhered, in order to improve the dispersibility of the carbon black. An activator may be added. As the surfactant, known surfactants in the rubber industry can be used, and examples thereof include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. It is done. Further, alcohol such as ethanol may be used instead of or in addition to the surfactant. However, when a surfactant is used, there is a concern that the rubber properties of the final vulcanized rubber will be lowered. Therefore, the amount of the surfactant to be blended is 100 mass of solid content (rubber) of the natural rubber latex solution. The amount is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and substantially no surfactant is used. Moreover, you may add an anti-aging agent in order to suppress deterioration of solid content (rubber) of a natural rubber latex solution in process (I) and process (II). As the anti-aging agent, anti-aging agents known in the rubber industry can be used, and examples thereof include amine-based, phenol-based, organic phosphite-based, and thioether-based agents.

  The carbon black to which the natural rubber latex particles are adhered in the slurry solution produced in the step (I) has a 90% volume particle size (μm) (“D90”) of preferably 31 μm or more, and more than 35 μm. It is more preferable. In this case, the dispersibility of the carbon black in the slurry solution is excellent and the reaggregation of the carbon black can be prevented, so that the storage stability of the slurry solution is excellent, and the low heat generation performance of the final vulcanized rubber, Excellent durability and rubber strength. In the present invention, D90 of the carbon black to which the natural rubber latex particles are attached means a value measured in addition to the carbon black and including the attached natural rubber latex particles.

(2) Step (II)
In step (II), the slurry solution and the remaining natural rubber latex solution are mixed to produce a carbon black-containing rubber latex solution to which the natural rubber latex particles are adhered. The method of mixing the slurry solution and the remaining natural rubber latex solution in a liquid phase is not particularly limited, and the slurry solution and the remaining natural rubber latex solution are mixed with a high shear mixer, a high shear mixer, a homomixer, and a ball mill. And a mixing method using a general disperser such as a bead mill, a high-pressure homogenizer, an ultrasonic homogenizer, and a colloid mill. If necessary, the entire mixing system such as a disperser may be heated during mixing.

  The remaining natural rubber latex solution preferably has a higher solid content (rubber) concentration than the natural rubber latex solution added in step (I), considering the drying time and labor in the next step (III). Specifically, the solid content (rubber) concentration is preferably 10 to 60% by mass, and more preferably 20 to 30% by mass.

(3) Step (III)
In the step (III), the carbon black-containing rubber latex solution to which the natural rubber latex particles are adhered is coagulated to produce a filler-containing rubber coagulated product. Examples of the coagulation method include a method in which a coagulant is contained in a carbon black-containing rubber latex solution to which natural rubber latex particles are adhered and coagulated.

  As the coagulant used in the coagulation step, acids such as formic acid and sulfuric acid usually used for coagulation of rubber latex solutions, and salts such as sodium chloride can be used.

  In the filler-containing rubber coagulated product obtained after step (III), the ratio of the rubber component to the filler is preferably 30 to 80 parts by mass of the filler with respect to 100 parts by mass (solid content) of the rubber. In this case, finally, a rubber wet masterbatch in which the degree of dispersion of the filler and the low heat generation performance and durability performance when vulcanized rubber is used can be improved in a balanced manner.

(Heating process)
In the heating step, the filler-containing rubber coagulum is dehydrated, dried and plasticized in one step by heating to 180 to 200 ° C. using a single screw extruder. FIG. 1 shows an example of a single-screw extruder that can be used in the present invention.

  The single screw extruder 20 includes a screw 23, an outer cylinder 27 including a first outer cylinder 25 located on the supply port 29 side (upstream side) and a second outer cylinder 26 located on the discharge port 30 side (downstream side). The filler-containing rubber coagulated product obtained after the coagulation step is introduced from the supply port 29, proceeds while being kneaded along the outer cylinder length direction (screw axis direction) 1, and finally is discharged 30 is discharged. The upstream portion is also referred to as a dewatering unit 21, and the downstream portion is also referred to as a drying unit (expander unit) 22. The drying unit 22 may be provided with a jacket 28 as necessary to adjust the temperature. However, in this invention, it is preferable not to have the pin part which protrudes from the inner cylinder inner wall surface of the drying part 22 to an inner diameter side. When the drying portion 22 has a pin portion, a high shearing force acts on the rubber component passing through the pin portion and causes the polymer chain in the rubber component to be broken, so that the deterioration of the rubber component is likely to proceed. As a result, the tear resistance of the finally obtained vulcanized rubber and the stress characteristics in a high strain region may be deteriorated. The screw shape of the single screw extruder, the length (L) of the outer cylinder (barrel), and the outer cylinder diameter (D) can be any single screw extruder used in the normal rubber industry. The ratio (L / D) between the outer cylinder length and the outer cylinder diameter can be arbitrarily set. The screw may be a heating screw.

  The inner wall surface of the outer cylinder 27 has at least one slit 24 extending along the outer cylinder length direction 1 (in this embodiment, as shown in FIG. 2 and FIG. However, a plurality of slits 24 are formed). As shown in FIG. 3, in the present embodiment, an example in which the slit 24 continuously extends along the outer cylinder length direction 1 is shown, but even if the slit 24 extends while being inclined with respect to the outer cylinder length direction 1. good. Furthermore, the slit 24 may extend from the supply port 29 side end of the outer cylinder 27 to the discharge port 30 side end, or may be formed only in the dehydrating part 21, and in the outer cylinder length direction 1. It may extend intermittently along. Moreover, as slit width D in an outer cylinder inner wall surface, 0.1-0.9 mm is illustrated, for example. FIG. 2 shows an example of the slit formed so that the slit width increases from the inner wall surface of the outer cylinder toward the slit depth direction. However, in the present invention, as the slit formed on the inner wall surface of the outer cylinder, A slit formed with a constant slit width from the inner wall surface to the slit depth direction may be used, or a slit formed so that the slit width may be narrowed.

  Blasting is performed on at least a part of the inner cylinder inner wall surface of the single-screw extruder. Specifically, as shown in FIG. 2, a portion 27 </ b> A where the slit 24 is not formed needs to be blasted on the inner cylinder inner wall surface. Of the inner wall surface of the outer cylinder, the portion 27A where the slit 24 is not formed is a surface that comes into contact with the filler-containing rubber coagulum during the heating process, and between the blasted surface and the screw, the filler-containing rubber coagulum. Shear force acts on. As a result, in the present invention, the filler-containing rubber coagulated material can be efficiently dehydrated, dried and plasticized in one step. The method of blasting the inner wall surface of the outer cylinder is not particularly limited, and physical polishing (shot blasting), chemical polishing (chemical corrosion) and the like can be used. As a projection material used for shot blasting, those known to those skilled in the art, such as sand, glass, and alumina, can be used. In order to suppress rubber deterioration and produce a rubber wet masterbatch excellent in elongation at break and tear resistance, the surface roughness (Ra) of the blasted surface of the inner wall surface of the outer cylinder after blasting is 10 to 10. The thickness is preferably 100 μm, and more preferably 20 to 60 μm.

  In the method for producing a rubber wet masterbatch according to the present invention, subsequent to the heating step, a kneading step and a vulcanizing compounding agent kneading step are carried out, various compounding agents are mixed into the rubber wet masterbatch, and the rubber composition is Can be manufactured.

(Kneading process)
Compound other than vulcanizing compound such as stearic acid, zinc white, anti-aging agent, silica, silane coupling agent, softener such as wax and oil, processing aid, etc. in rubber wet masterbatch obtained after heating process A process in which an agent is added and kneaded using a mixing and dispersing machine. In the kneading process, these compounding ingredients are mixed with the rubber component to increase the strength of the rubber product after vulcanization, to improve the rubber kneading performance, resulting from radicals generated by the breaking of rubber molecular chains The effect of preventing deterioration of the rubber is obtained. In the kneading step, a meshing Banbury mixer, a tangential Banbury mixer, a kneader, or the like can be used, and it is particularly preferable to use a meshing Banbury mixer.

  As an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone-based anti-aging agent, a monophenol-based anti-aging agent, a bisphenol-based anti-aging agent, a polyphenol-based anti-aging agent, dithiocarbamic acid, which are usually used for rubber Anti-aging agents such as a salt-based anti-aging agent and a thiourea-based anti-aging agent may be used alone or in an appropriate mixture. The content of the antioxidant is more preferably 0.3 to 3 parts by mass, and 0.5 to 1.5 parts by mass with respect to 100 parts by mass of the rubber component (solid content) of the rubber wet masterbatch. More preferably it is.

(Vulcanization system compounding process)
A vulcanizing compounding agent such as a vulcanizing agent such as sulfur or a vulcanization accelerator is added to the rubber composition obtained after the kneading step, and the whole is kneaded. When the rubber composition obtained after the vulcanizing compounding agent kneading step is heated to a predetermined temperature or more, the vulcanizing agent in the rubber composition reacts with the rubber molecules, forms a bridge structure between the rubber molecules, and the molecules A three-dimensional network is formed to give rubber elasticity.

  Sulfur should just be normal sulfur for rubber | gum, For example, powder sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur etc. can be used. The content of sulfur in the rubber composition according to the present invention is preferably 0.3 to 6 parts by mass with respect to 100 parts by mass of the rubber component. When the sulfur content is less than 0.3 parts by mass, the crosslinking density of the vulcanized rubber is insufficient and the rubber strength is lowered. When the content exceeds 6.5 parts by mass, both heat resistance and durability are particularly high. Getting worse. In order to secure the rubber strength of the vulcanized rubber and improve the heat resistance and durability, the sulfur content should be 1.5 to 5.5 parts by mass with respect to 100 parts by mass of the rubber component. Is more preferable.

  As the vulcanization accelerator, sulfenamide vulcanization accelerator, thiuram vulcanization accelerator, thiazole vulcanization accelerator, thiourea vulcanization accelerator, guanidine vulcanization, which are usually used for rubber vulcanization. Vulcanization accelerators such as accelerators and dithiocarbamate vulcanization accelerators may be used alone or in admixture as appropriate. As for content of a vulcanization accelerator, it is more preferable that it is 1-5 mass parts with respect to 100 mass parts of rubber components, and it is further more preferable that it is 1.5-4 mass parts.

  Hereinafter, the present invention will be described in more detail with reference to examples. The raw materials used and the equipment used are as follows.

(Raw materials used)
a) Carbon black
Carbon black “N330”; “Seast 3” (manufactured by Tokai Carbon Co., Ltd.)
Carbon black “N110”; “Seast 9” (manufactured by Tokai Carbon Co., Ltd.)
Carbon black “N774”; “Seast SO” (manufactured by Tokai Carbon Co., Ltd.)
b) Dispersion solvent Water c) Rubber latex solution Natural rubber concentrated latex solution; manufactured by Regex Corporation ((DRC (Dry Rubber Content)) = 60%, mass average molecular weight 236,000) and water at room temperature to add rubber component 25 Natural rubber fresh latex solution (Golden Hope) ((DRC (Dry Rubber Content)) = 31.2%, weight average molecular weight 232,000) and water added at room temperature to 25 mass of rubber component D) Coagulant Formic acid (primary 85%, 10% solution diluted to pH 1.2), “manufactured by Nacalai Tesque”
e) Zinc flower
(A) No. 1 zinc white (Mitsui Metals)
(B) No. 3 zinc white (Mitsui Metals)
f) Stearic acid (manufactured by NOF Corporation)
g) Wax (Nippon Seiwa Co., Ltd.)
h) Anti-aging agent (A) Aromatic amine type: N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine “6PPD” (manufactured by Monsanto), melting point 44 ° C.
(B) Amine Kenton series: 2,2,4-trimethyl-1,2-dihydroquinoline polymer “RD” (manufactured by Ouchi Shinsei Chemical), melting point 80-100 ° C.
i) Sulfur
(A) Sulfur (made by Tsurumi Chemical Co., Ltd.)
(B) Insoluble sulfur “OT-20” (manufactured by Akzo)
j) Vulcanization accelerator (A) "CBS" (manufactured by Sanshin Chemical Co., Ltd.)
(B) N, N-dicyclohexylbenzothiazole-2-sulfenamide “Noxeller DZ” (Ouchi Shinsei Chemical Co., Ltd.)
k) Boron-containing organic acid cobalt “Manobond C680C” (manufactured by OMG)
l) Resorcin-alkylphenol-formalin resin “SUMIKANOL 620” (manufactured by Sumitomo Chemical Co., Ltd.)
m) Hexamethoxymethyl melamine “Ciretz 963L” (Mitsui Cytec)
n) Additional rubber High cis polybutadiene rubber “BR150L” (manufactured by Ube Industries)

(Evaluation)
The evaluation was performed on rubber obtained by heating and vulcanizing each rubber composition at 150 ° C. for 30 minutes using a predetermined mold.

(Moisture content of filler-containing rubber coagulum)
Based on JIS K6238-2, it measured using A & D company heat drying type moisture meter MX-50.

(Mooney viscosity of rubber wet masterbatch)
The measurement was performed at 100 ° C. in accordance with JIS K6300. The evaluation was performed with the index of Comparative Example 1 being 100. The lower the value, the better the plasticization.

(Surface roughness of blasted surface (Ra))
In accordance with JIS B0601, using a laser microscope (ultra-deep shape measurement microscope VK-8500 (manufactured by KEYENCE)), 10 randomly extracted metal surfaces were observed, and image measurement analysis software (VK-H1W) The surface roughness was measured by (manufactured by KEYENCE Corporation), and the average value was calculated to determine the arithmetic average surface roughness (Ra) of the blasted surface.

(Elongation at break of vulcanized rubber)
In accordance with JIS-K 6251, an evaluation sample was prepared using a JIS No. 3 dumbbell, and the elongation at break was measured. Evaluation is performed with respect to Examples 1 to 2 and Comparative Examples 1 to 5, with Comparative Example 1 as 100, and with Examples 3 and 4, Comparative Example 6 is performed as 100, and Comparative Example 6 is compared. The index evaluation is performed with Example 7 as 100, and the higher the numerical value, the better the rubber physical properties are, and the better the rubber properties are.

(Tear resistance)
An evaluation sample was prepared in accordance with JIS K6252 and its tear resistance was evaluated. Evaluation is performed with respect to Examples 1 to 2 and Comparative Examples 1 to 5, with Comparative Example 1 as 100, and with Examples 3 and 4, Comparative Example 6 is performed as 100, and Comparative Example 6 is compared. The index evaluation is performed with Example 7 as 100, and the higher the value, the better the tear resistance.

Example 1
70 parts by mass of carbon black was added to a diluted natural rubber latex solution adjusted to 0.5% by mass (the solid content of the latex solution (amount of rubber) was 1 part by mass with respect to the carbon black). A carbon black-containing slurry solution to which the natural rubber latex particles were adhered was produced by dispersing carbon black using Robomix (conditions of the Robomix: 9000 rpm, 30 minutes) (Step (I)).

  Next, water is added to the remaining natural rubber concentrated latex solution (solid content (rubber) concentration of 25 mass%) to the carbon black-containing slurry solution to which the natural rubber latex particles produced in the step (I) are attached. And the natural rubber latex solution used in step (I) is added so that the solid content (rubber) amount is 100 parts by mass, and then a household mixer SM-L56 manufactured by SANYO Co., Ltd. is used. Mixing was performed using a mold (conditions of the mixer: 11300 rpm, 30 minutes) to produce a carbon black-containing natural rubber latex solution to which the natural rubber latex particles were adhered (step (II)).

(Coagulation process)
A carbon black-containing natural rubber coagulated product is added to the carbon black-containing natural rubber latex solution to which the natural rubber latex particles produced in the step (II) are attached, until a pH of 4 is obtained by adding a 10% by weight aqueous solution of formic acid as a coagulant. Produced (step (III)).

(Heating process)
1 to 3 squeezer type single screw extruder (manufactured by Suehiro EPM, part number V-02), barrel diameter 90 mm, (barrel length) / (barrel diameter) (L / D) = 8.6 The surface roughness (Ra) of the blasted surface 27A is 34 μm, the slit width D = 0.7 mm, 0.5 mm, 0.2 mm on the inner wall surface of the outer cylinder, and the heating temperature is 200 ° C. (heating of the heating screw) Dehydration, drying, and plasticization were performed in one step while kneading at a temperature of 200 ° C. The outer cylinder inner wall surface 27A was blasted by treating alumina particles of φ0.8 mm at a blast pressure of 0.4 MPa.

(Kneading process and vulcanizing compound compounding process)
For the obtained natural rubber wet masterbatch, a B-type Banbury mixer (manufactured by Kobe Steel Co., Ltd.) was used, and various additives listed in Table 1 were blended to form a rubber composition, and the physical properties of the vulcanized rubber were measured. did. The results are shown in Table 1.

Examples 2-5
Natural rubber wet masterbatch, rubber composition, and vulcanized rubber by the same method as in Example 1 except that the type of carbon black used, the heating temperature in the heating step, and the types and amounts of various additives were changed. Manufactured.

Comparative Example 1
Instead of heating process, dehydration process (dehydration temperature (heating screw temperature of single screw extruder used during dehydration): 160 ° C) and dry plasticization process (dry plasticization temperature (single screw extrusion used during dry plasticization) The heating type screw temperature of the machine): 160 ° C) was carried out, and the same as in Example 1 except that the inner wall surface of the outer cylinder of the single-screw extruder used in these steps was not blasted A natural rubber wet masterbatch, a rubber composition and a vulcanized rubber were produced by the method. Table 1 shows the physical properties of the vulcanized rubber.

Comparative Examples 6 and 7
A natural rubber wet masterbatch, a rubber composition and a vulcanized rubber were produced in the same manner as in Comparative Example 1 except that the type of carbon black used and the types and amounts of various additives were changed.

Comparative Examples 2 and 3
A natural rubber wet masterbatch, a rubber composition and a vulcanized rubber were produced in the same manner as in Example 1 except that the blast treatment was not performed on the inner cylinder inner wall surface of the single screw extruder used in the heating step. Table 1 shows the physical properties of the vulcanized rubber.

Comparative Examples 4 and 5
A natural rubber wet masterbatch, a rubber composition and a vulcanized rubber were produced in the same manner as in Example 1 except that the heating temperature in the heating step was changed. Table 1 shows the physical properties of the vulcanized rubber.

  From the results in Table 1, the rubber wet master batches according to Examples 1 to 5 have a sufficiently low moisture content in only one heating step as compared with the rubber wet master batches according to Comparative Examples 1, 6, and 7. doing. Further, the Mooney viscosity is also decreased, and it can be seen that plasticization is sufficiently performed. Furthermore, it can be seen that the elongation at break and the tear resistance are improved when a vulcanized rubber is used. On the other hand, the rubber wet masterbatch according to Comparative Example 2 is manufactured using a single-screw extruder that is not subjected to blasting on the inner wall surface of the outer cylinder, and thus has a high moisture content after the heating step, It can be seen that the plasticization is insufficient. Moreover, since the rubber wet masterbatch which concerns on the comparative example 3 was manufactured raising the heating temperature to 220 degreeC compared with the comparative example 2, a moisture content is low and plasticization is fully performed. However, it can be seen that the rubber component deteriorates with high-temperature treatment, and the vulcanized rubber elongation at break and tear resistance deteriorate.

  Moreover, since the rubber wet masterbatch which concerns on the comparative example 4 was low in heating temperature, the moisture content was very high and plasticization was also inadequate. As a result, kneading could not be performed in the kneading step, and physical properties of the vulcanized rubber could not be measured. Furthermore, since the rubber wet masterbatch which concerns on the comparative example 5 has high heating temperature, it turns out that a rubber component deteriorates with a high temperature process, and the elongation at break and tear resistance of vulcanized rubber deteriorate.

Claims (2)

A method for producing a rubber wet masterbatch obtained using at least a filler, a dispersion solvent, and a rubber latex solution as raw materials,
A coagulation step for producing a filler-containing rubber coagulum by mixing and coagulating the slurry solution containing the filler and the dispersion solvent and the rubber latex solution;
A heating step in which the filler-containing rubber coagulum is dehydrated, dried and plasticized in one step by heating to 180 to 200 ° C using a single screw extruder,
The single-screw extruder has a screw and an outer cylinder in which a slit extending along the outer cylinder length direction (screw axis direction) is formed on the inner wall surface, and at least a part of the inner cylinder inner wall surface is blasted A method for producing a rubber wet masterbatch, wherein   2. The method for producing a rubber wet masterbatch according to claim 1, wherein a surface roughness (Ra) of a blasted surface of the inner wall surface of the outer cylinder is 10 to 100 μm.

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